Compositions based on aqueous dispersions jof bitumen and polyurethane method for the preparation thereof and uses thereof

ABSTRACT

The invention relates to an aqueous polymer composition containing at least one aqueous bitumen dispersion and at least one aqueous dispersion of at least one polyurethane obtained from a polyol component which contains at least one hydroxylated polydiene, a method for the preparation thereof by simply mixing two aqueous dispersions, and the use of said composition in several applications such as the productions of surface dressings, waterproof layers applied underneath road surface dressings, watertight roof coatings, road surface dressings, and sound damping and shock absorbing or insulating coatings. Bitumen that has been modified according to the inventive method has a very high threshold and improved mechanical properties. The inventive aqueous dispersions is also stable during storing and makes it possible to obtain a film by simply evaporating water.

The present invention relates to the field of emulsified asphalts, inparticular to the field of asphalts in the form of an emulsion (oraqueous dispersion) that are modified by an aqueous polymer dispersionand more particularly to the field of emulsified asphalts modified by anaqueous dispersion of a specific polyurethane.

The use of asphalt-polymer blends is well known, particularly in theroad field and in the waterproofing field, in particular in the form ofmembranes and coatings. The incorporation of polymers into asphaltsmodifies their properties so as to improve the thermal behaviour, whichis characterized by an increase in the flow (creep) temperature and by areduction in the stiffening (cracking) temperature, with as aconsequence an improvement in the elongation, the tensile strength andthe tear strength.

Among the various industrial applications of asphalt emulsions, mentionmay be made, for example, of the production of surface coats, waterproofcourses under asphalt road mixes, asphalt road mixes, slurry seals orcold cast mixes, agglomeration binders, protective coverings for pipes,carpet underlay impregnation and tie layers, soundproofing and dampingcoverings. In all cases, these involve a dispersion of asphalt orbituminous substance in an aqueous phase obtained using a surfactant andby supplying energy provided either by a colloidal mill or by any otherdevice suitable for forming the dispersion. In general, and depending onthe type of emulsifier used in preparing the emulsion, two types ofemulsions may be distinguished, namely anionic aqueous emulsions andcationic aqueous emulsions.

The first (i.e. anionic) emulsions generally find their applications inthe building and public works (BPW) sector or the construction and civilengineering sector for waterproof membranes, bonding coats and externalprotective coatings. In particular, they are very widely used in thefield of roofing membranes (for flat roofs and built-up roofs). Theessential properties for these applications are the elasticity of theasphalt, good high-temperature resistance (low creep) and goodlow-temperature resistance (cracking resistance), and also good adhesionto steel and concrete substrates and low water absorption (i.e. goodimpermeability). This is because the asphalts used in roofing membranesmust withstand large seasonal variations in temperature with lifetimesof several years. Emulsified asphalts not modified by a polymer additivedo not in general result in satisfactory performance. This is becausethe mechanical properties of asphalts are very temperature-sensitive.They often become too rigid and brittle at winter temperatures, whereasthey have a tendency to creep at high temperatures, for example in thesummer. Moreover, asphalts generally have a low adhesion to conventionalsubstrates, such as concrete and steel. It is therefore often necessaryto apply a primer layer, which entails additional production costs.Finally, their impermeability and their chemical resistance are ofteninsufficient.

The second (i.e. cationic) emulsions are used in general as a binder inthe construction or repair of road pavements. The properties that it isdesired to improve are therefore the rutting resistance (i.e. theability of the asphalt to withstand abrasion, creep and ageing inducedby vehicular traffic), low-temperature cracking resistance and adhesionto the aggregates.

U.S. Pat. No. 4,724,245 discloses a method that consists in preparing ablend of asphalt and hydroxytelechelic polybutadiene denoted hereafterby HTBD, and in emulsifying it in aqueous phase, the crosslinking takingplace by addition of polyisocyanate dispersed in aqueous phase.

U.S. Pat. No. 3,909,474 discloses a similar method based on apreoxidized asphalt, the crosslinking taking place by oxidation of theHTBD.

U.S. Pat. No. 3,932,331 discloses a method for rapidly breaking andhardening an asphalt emulsion by incorporating therein an isocyanate(NCO)-terminated urethane prepolymer. When the prepolymer is added tothe asphalt emulsion, this makes it impossible to store theasphalt-polymer emulsion blend since the isocyanate reacts with thewater of the emulsion.

DE 40939151 discloses a composition obtained by the reaction of aprepolymer with a dispersion of an unsaturated olefin compound, ofpolyurethane or of asphalt.

DE 4408154 discloses a coating based on an asphalt emulsion containing apolyurethane prepolymer with NCO terminal groups.

Most of these methods, known in the prior art, require the use ofreactive two-component (2K) compositions with the necessary presence ofan isocyanate component and strict control of the operating conditionsboth from the environmental/health/safety standpoint and the technicalstandpoint in terms of strict dosing of the reactive components in orderto achieve satisfactory performance. More particularly, owing to theapplication conditions often imposed (e.g. environmental constraints:temperature and humidity), the structure and the applicative performanceof the end product are often very difficult to reproduce. Moreover, thechanging reaction of the isocyanate component may very well disturb thefragile stability of the dispersion in its entirety.

The present invention remedies these problems by proposing a solutionbased on an aqueous polymer composition equivalent to a nonreactiveone-component (1 K) composition. Indeed, there is complete absence of areactive component liable to be affected by the operating conditionsduring application or to affect its processing conditions in terms ofhealth, safety or the environment by its use.

The first subject of the present invention is therefore an aqueouspolymer composition comprising:

-   a) at least one aqueous asphalt dispersion; and-   b) at least one aqueous dispersion of at least one polyurethane,    this polyurethane being obtained from a polyol component containing    at least one hydroxylated polydiene.

Another subject of the invention is a method of preparation of thecomposition defined according to the invention, by simple physicalblending of an aqueous asphalt dispersion with an aqueous polyurethanedispersion, the two emulsions being compatible. This method makes itpossible to modify the asphalt and to improve all of its properties, andconsequently to offer novel technical solutions in the BPW membranesector and the construction and civil engineering sector. This methodhas the advantage of proposing a one-component system containing no freeisocyanate (free NCO), which is homogeneous and stable. In addition, theasphalt-polymer film forms and hardens by simple water evaporation underthe ambient application conditions.

Another subject of the invention is a coating composition comprising atleast one aqueous polymer composition as defined according to theinvention.

Another subject of the invention is the use of an aqueous polymercomposition of the invention in the production of surface coats,waterproof courses under asphalt road mixes, roofing membranes, asphaltroad mixes, slurry seals or cold cast mixes, agglomeration binders,protective coverings for pipes, carpet underlay impregnation and tielayers, soundproofing and damping or insulating coverings.

The invention also relates to a method of use of the aqueous polymercomposition as defined according to the invention, which comprises thefollowing steps:

-   a) blending of at least one aqueous asphalt dispersion with at least    one aqueous dispersion of at least one polyurethane as defined    according to the invention;-   b) direct application of the blend obtained in step a) to the    application object or substrate;-   c) drying/film-forming by simple water evaporation; it being    possible for the three steps a), b) and c) to be carried out on the    actual site of the application and under the ambient conditions of    the application site.-   A final subject of the invention relates to end products such as    coatings, surface coats, waterproof courses under asphalt road    mixes, roofing membranes, asphalt road mixes, slurry seals or cold    cast mixes, agglomeration binders, protective coverings for pipes,    carpet underlay impregnation and tie layers, soundproofing and    damping or insulating coverings obtained according to the method of    use of the invention or from an aqueous polymer dispersion    composition as defined according to the invention.

Specifically, the Applicant has discovered that the addition of anaqueous polyurethane dispersion, denoted hereafter by PUD, into anaqueous asphalt dispersion (emulsion) makes it possible to obtain astorage-stable blend and to very significantly improve the mechanicalperformance in terms of thermal withstand at low and high temperatures(stiffening problem and creep resistance) and in particular themechanical properties, such as the tensile strength and the elongationat the break of the modified asphalt that results from the presence ofthe PUD. In addition, the properties of adhesion of the asphalt to steelor concrete are considerably improved, as is the water vaporimpermeability for applications such as membrane or sealing layers.

The Applicant has also discovered that when the polyurethane dispersionis produced from a hydroxytelechelic polybutadiene (HTBD), the chemicalresistance properties are particularly improved.

According to the invention, the aqueous polyurethane dispersion may beprepared using a method described in WO 99/4894, which comprises thefollowing steps:

-   -   (a) formation of a prepolymer having NCO functional groups by        reaction in a solvent:        -   of a polyisocyanate component, and        -   of a polyol component comprising a diol, carrying at least            one neutralized acid functional group, the NCO functional            groups being in excess relative to the OH functional groups,            and in a ratio of between 1.5 and 2.5,    -   (b) dispersion of the prepolymer in water,    -   (c) addition of a diamine-type chain extender, and    -   (d) evaporation of the solvent in order to obtain an aqueous        polyurethane dispersion containing urea functional groups.

The polyurethane component of the aqueous polymer dispersion compositionaccording to the invention represents from 2 to 50% and preferably from5 to 25% by weight relative to the total asphalt+polyurethane weight,the weight being expressed as dry matter.

Preferably, the hydroxylated polydiene is chosen from hydroxytelechelicconjugated-diene oligomers that can be obtained by various methods suchas the radical polymerization of conjugated dienes having from 4 to 20carbon atoms in the presence of a polymerization initiator, such ashydrogen peroxide or an azo compound, such as2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], or the anionicpolymerization of conjugated dienes having from 4 to 20 carbon atoms inthe presence of a catalyst, such as dilithium naphthalene.

According to the present invention, the polyol component of thepolyurethane consists of at least 50% and preferably at least 80% byweight of at least one hydroxytelechelic conjugated-diene oligomer. Thisis preferably selected from hydroxytelechelic oligomers derived from:butadiene, isoprene, chloroprene, 1,3-pentadiene, cyclopentadiene andmixtures thereof. The number-average molecular weight of the oligomersthat can be used may vary from 500 to 15 000 and preferably from 1000 to3000, the hydroxyl number expressed in milliequivalents per gram (meq/g)is from 0.5 to 5 and preferably from 0.7 to 1.8, and their viscosity isbetween 1000 and 10 000 mpa.s.

Preferably, a butadiene-based and more particularly hydroxytelechelicpolydiene-polyol will be used. Advantageously, the polydiene-polyolcomprises 70 to 85 mol %, preferably 80 mol %, of 1-4 units and 15 to 30mol %, preferably 20 mol % of 1-2 units. As an illustration ofpolydiene-polyols, mention may be made of hydroxyl-terminatedpolybutadiene sold by Atofina under the brand names PolyBd®R45 HT andPolyBd®R20 LM. Hydroxylated copolymers of conjugated dienes with vinyland/or acrylic monomers, such as styrene or acrylonitrile, may also besuitable as hydroxylated polydienes. Likewise, in-chain-epoxidizedhydroxytelechelic butadiene oligomers or else hydroxytelechelicconjugated-diene oligomers, when partially or completely hydrogenated,may be suitable for this use.

The diol carrying at least one neutralized acid functional group may betriethylamine-neutralized dimethylolpropionic acid.

A short diol may also form part of the polyol component used for thepreparation of the polyurethane. As examples of such diols, mention maybe made of 2-ethyl-1,3-hexanediol, N,N′-bis(2-hydroxypropyl) aniline.The amount of such a diol is advantageously between 1 and 30 parts byweight per 100 parts of hydroxyl-terminated polydiene.

According to the present invention, the polyisocyanate used for thepreparation of the aqueous polyurethane dispersion may be an aromatic,aliphatic or cycloaliphatic polyisocyanate having at least twoisocyanate functional groups in its molecule.

A way of illustration of aromatic polyisocyanates, mention may be madeof 4,4′-diphenylmethane diisocyanate (MDI), liquid modified MDIs,polymeric MDIs, 2,4- and 2,6-tolylene diisocyanate (TDI) and mixturesthereof, xylylene diisocyanate (XDI), triphenylmethane triisocyanate,tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate(PPDI) and naphthalene diisocyanate (NDI).

Among the aromatic polyisocyanates, the invention preferably relates to4,4′-diphenylmethane diisocyanate and most particularly to liquidmodified MDIs.

By way of illustration of aliphatic polyisocyanates, mention may be madeof hexamethylene diisocyanate (HDI), and its derivatives,trimethylhexamethylene diisocyanate.

By way of illustration of cycloaliphatic polyisocyanates, mention may bemade of isophorone diisocyanate (IPDI), and its derivatives,4,4′-dicyclohexylmethane diisocyanate and cyclohexyl diisocyanate(CHDI).

A catalyst may be added, which may be chosen from the group comprisingtertiary amines, imidazoles and organometallic compounds.

By way of illustration of a tertiary amine, mention may be made ofdiaza-1,4-bicyclo[2.2.2]octane (DABCO).

By way of illustration of organometallic compounds, mention may be madeof dibutyltindilaurate and dibutyltindiacetate.

The amounts of catalyst may be between 0.01 and 5 parts by weight per100 parts by weight of polyol (hydroxyl-teminated polydiene and diolwith an acid functional group).

The amount of isocyanate is advantageously such that the NCO/OH molarratio is greater than 1.4 and preferably between 1.5 and 2.5. The OHfunctional groups are those of hydroxylated polydiene and of the diolwith an acid functional group and of the short diol.

The amount of diol containing neutralized acid functional groups isadvantageously such that there are 0.2 to 2.5 carboxylate functionalgroups per hydroxyl-terminated polydiene chain. The presence of asolvent is necessary in order to allow the prepolymer to be synthesized,this solvent having to be easy to remove in step (d). It is preferred touse methyl ethyl ketone (MEK). This step (a) is carried out inconventional stirred reactors.

The amount of water in step (b) is such that, in step (d), a dispersioncontaining from 20 to 60 and preferably from 30 to 50 wt % of solidmatter (SC:Solids Content) is obtained. In step (b), the water isadvantageously introduced into a stirred reactor. This step (b) may ormay not be carried out under pressure, but it is simpler to be atatmospheric pressure. The temperature of this step may vary from roomtemperature (20° C.) to 80° C., and it is preferably at room temperature(20° C.).

As chain extender in step (c), mention may be made of a diamine-typeextender and more particularly hydrazine in aqueous solution orethylenediamine or isophoronediamine or hydroxylamine. The extensionreaction may be carried out at a temperature ranging from roomtemperature to 80° C., and preferably at room temperature and atatmospheric pressure. The extension of the chains in the dispersion maybe monitored by volumetric analysis of the isocyanate functional groupsover the course of time. The reaction time is around 10 minutes.

Step (d) may be carried out, for example, by a distillation using astandard device.

The aqueous dispersions obtained do not contain a substantial amount ofsolvent (preferably less than 5%), they have a low viscosity, forexample from 4 to 10 mpa.s and they have a solids content (SC) of 20 to60% and preferably of 30 to 50% by weight.

As regards the method of preparation of the aqueous polymer compositionaccording to the invention, the proportions of the respective asphaltand polyurethane dispersions are in a weight ratio ranging from 2 to 75%of dispersion, for asphalt and polyurethane dispersions having solidscontents that can be independently varied within a range from 20 to 60%by weight, and preferably from 30 to 50% by weight, of each dispersion.

As regards the coating compositions according to the invention, thesemay serve for the production of coatings or coats for protection,sealing or waterproofing, soundproofing, or damping, for road and roofapplications, in buildings or in industry.

The following examples illustrate the invention without limiting thescope thereof.

EXAMPLES

An aqueous polyurethane dispersion was typically obtained from anisocyanate-terminated urethane prepolymer containing anionic (i.e.carboxylic) or cationic functional groups so as to allow emulsification.This prepolymer was firstly neutralized and dispersed in water. The nextstep consisted in increasing the molecular weight or carrying out achain extension by the addition of a diamine in order to obtain apolyurea polyurethane (PUD) dispersion. It would have been possible, forexample, without this being restrictive as regards the type of PUDcovered by the present patent, to choose an anionic PUD obtained from ahydroxylated polybutadiene as described in patent application Ser. No.FR 98/03793. Aqueous polyurethane dispersion Composition Anionicpolyurethane dispersion based on hydroxylated polybutadiene (PolyBdR45HT ® from Atofina) Solids content 37.9% by weight pH 7.3

This aqueous polyurethane dispersion was added to an asphalt in aqueousemulsion with an uncharged cellular structure (the emulsion being ableto be used as a multipurpose asphalt-based coating for sealing, bonding,insulating, protecting and tiling). These two emulsions were blended atroom temperature using a blade stirrer rotating at low speed for 10minutes in the following proportions by weight [m1, m2]: [0, 100], [5,95], [10, 90], [20, 80], [50,50], [75, 25] and [100, 0], where m1represents the mass of aqueous PUD polyurethane dispersion and m2 themass of asphalt emulsion. Asphalt emulsion Composition Anionic asphaltemulsion Solids content 48% by weight pH 9.5Storage Stability

The storage stability of the emulsion blends was monitored over a periodof 1 month at room temperature. It was possible to obtain stable blendswith PUD contents ranging up to 50 parts by weight per 50 parts byweight of asphalt dispersion, no phase separation being observed. Thestorage stability is therefore deemed to be good. The results are givenin detail in Table 1 below. TABLE 1 Evaluation of the stability of theblend as a function of the PUD/asphalt dispersion composition afterbeing stored for one month. PUD (parts by weight)  0  5 10 20 50 75 100Asphalt emulsion 100 95 90 80 50 25  0 (parts by weight) 1 month at roomSta- Sta- Sta- Sta- Sta- Un- sta- temperature ble ble ble ble ble stablebleEvaluation of the Hot and Cold Properties

All the specimens were analyzed by DMA so as to monitor the change inthe properties with temperature and more precisely to determine theinfluence of the PUD modifier content on the upper and lower operatinglimits of the asphalt. The moduli E′ (dynamic storage modulus) and E″(dynamic loss modulus), and also the loss factor tan δ(=E″/E′), weremeasured by DMA analysis between −100° C. and +100° C. at a frequency ωof 10 rad.s⁻¹.

A high temperature limit was able to be demonstrated. This temperaturecorresponds to the flow point of the asphalt, and beyond this point theproperties of the specimen could no longer be measured and the test wastherefore stopped. In the case of the [100/0] asphalt, the flow point,as defined above, was at T[100/0]=31° C. This temperature clearlyincreases when the bitumen is modified by the PUD (“asphaltemulsion”/“PUD” parts by weight in brackets). Thus, a T[95/5] of 54.7°C. was obtained and then a T[90/10] of 66.7° C. and a T[80/20]>100° C.were obtained, as indicated in Table 2.

As in the case of the determination of a low temperature limit, we set astiffening criterion T* as being the temperature at which the modulus E′(dynamic storage modulus determined by DMA at the frequency ω of 10rad.s−1) of the modified asphalt increases by half a decade relative tothe modulus E′ at room temperature (RT=20° C.). According to thiscriterion, we therefore obtained a T* [100/0] of +4° C. in the case ofthe control asphalt and then a T* [95/5] of −18.1° C., a T* [90/10] of−9.9° C., a T* [80/20] of −11.9° C., a T* [50/50] of −32.6° C. andfinally a T* [25/75] of −53.3° C. in the case of the modified asphalts.TABLE 2 Measurement of the flow and stiffening temperatures as afunction of the PUD/asphalt dispersion composition (PU: drypolyurethane) Anionic HTBD-based 0 5 10 20 50 75 100 polyurethanedisper- sion (parts by weight) Anionic asphalt emul- 100 95 90 80 50 250 sion (parts by weight) Amount in % of dry 0 3.98 8.06 16.48 44.1271.64 100 polyurethane (PU) in the blend (solids ratio by weight) T(flow point) ° C. 31 54.7 66.7 >100 >100 >100 >100 T* (stiffening ° C. 4−18.1 −9.9 −11.9 −32.6 −53.3 −62.2 point)

These measurements clearly show that the plasticity range of the controlasphalt is widened by the use of PUD as modifier. The high-temperatureproperties (i.e. creep) are improved as is the low-temperature crackingresistance.

Evaluation of the Adhesion to Steel

The various PUD-modified asphalt emulsions were then applied as a 1 mmthick film to steel. The steel substrate selected was a conventionalsteel (low-carbon mild steel) surface-treated beforehand by shotpeening. An adhesion-to-steel test was carried out according to theRenault D51 1755 standard, which consists in adhesively bonding acircular stud with a diameter Ø of 20 mm to the coating by means of atwo-component epoxy adhesive (ARALDITE from Ciba-Geigy). This stud wasthen pulled at a rate of 10 mm/min on a tensile testing machine in thearrangement described below. The maximum tear force and the failure mode(cohesive or adhesive failure) were then noted.

The asphalt alone showed only very weak adhesion to shot-peened steel.When the amount of modifier was increased, the adhesion improved verysubstantially. An adhesion of 1.38 MPa obtained for the [5/95]PUD/asphalt emulsion blend was 1.38 MPa, then 3.37 MPa for the [20/80]blend and greater than 4 MPa for the [50/50] and [75/25] blends. Theresults are given in Table 3.

Evaluation of the Adhesion to Concrete

For these tests, we used concrete slabs of dimension 40×40×5 cm of theLUCIANA reference type. They were dedusted and rinsed in waterbeforehand, and then placed for at least 24 hours in fan oven at 50° C.in order to dry them. The various PUD-modified emulsions were thenpoured onto the concrete slab to form a coating about 1 mm in thickness.The coated slab was left for one week at ambient temperature andhumidity. An adhesion test as described above was then carried out. Theresults confirmed that the adhesion properties of the asphalt areimproved by the addition of PUD, particularly with contents of between10 and 20%, for which cohesive failure in the concrete substrate wasobserved. The results are given in the summarizing Table 3.

Evaluation of the Water Vapor Permeability

Films 2 mm in thickness were produced from the various PUD-modifiedasphalt emulsions. The specimens were placed for 2 hours in a fan ovenat 50° C. and then for one week at room temperature in the laboratory inorder to complete the film-forming process, before being cut into testpieces. The water vapor permeability measurements were carried outaccording to the ASTM E 96 E standard (38° C./90% relative humidity RH).A considerable improvement in the impermeability properties of the filmwas observed thanks to the use of PUD. The results are given in thesummarizing Table 3.

Evaluation of the Mechanical Properties

Films 2 mm in thickness were produced from the various PUD-modifiedasphalt emulsions. The specimens were placed for 2 hours in a fan ovenat 50° C. and then for one week at room temperature in the laboratory inorder to complete the film-forming process, before being cut into testpieces for the mechanical tests. The tensile strength was almost zero inthe case of bitumen alone, whereas values well above 1 MPa were obtainedwith a dry PU (polyurethane) modifier polymer content of around 16%.This tensile strength, like the elongation at break, increases withincreased PU modifier polymer content (see Table 3). TABLE 3 Summary ofthe properties of the modified asphalts as a function of the PUD/asphaltdispersion composition Anionic HTBD-based 0 5 10 20 50 75 100polyurethane dispersion (parts by weight) Anionic asphalt emulsion 10095 90 80 50 25 0 (parts by weight) Dry PU content in the 0 3.98 8.0616.48 44.12 71.64 100 blend (amount by weight per 100 parts of solids)Adhesion to steel MPa 0 1.38 — 3.37 4.63 4.16 7.9 (Renault D51 cohesivecohesive cohesive cohesive 1755) asphalt asphalt asphalt asphaltAdhesion to kN 2.66 2.77 3.48 3.04 3.13 1.95 2.13 concrete (Renaultcohesive cohesive cohesive cohesive cohesive adhesive adhesive D51 1755)asphalt asphalt concrete concrete concrete Water vapor g.500 μm/mm²295.2 247.5 102.4 103.38 16.68 15.7 26 permeability 24 h (ASTM E96E)Tensile strength MPa ≈0 ≈0 ≈0 1.4 2.1 2.6 5.1 (ASTM D412-98a) Elongationat % ≈0 ≈0 ≈0 19 80 265 413 break (ASTM D624- 00e1) Tear strength N/mmNot Not Not 13.7 17.1 17.8 21.6 (ASTM 2240-00) measurable measurablemeasurable Hardness Shore A Not Not Not 63 70 69 70 measurablemeasurable measurable T (flow point) ° C. 31 54.766.7 >100° >100° >100° >100° T* (stiffening ° C. 4 −18.1 −9.9 −11.9−32.6 −53.3 −62.2 point)

1. A aqueous polymer composition comprising a simple mixture of: a) at least one aqueous asphalt dispersion; and b) at least one aqueous dispersion of at least one polyurethane, said polyurethane being obtained from a polyol component comprising at least one hydroxylated polydiene, said aqueous polyurethane dispersion having previously and separately been prepared according to the following steps: (a) formation of a prepolymer having NCO functional groups by reaction in a solvent of a polyisocyanate component, and a polyol component comprising a diol containing at least one neutralized acid functional group, (b) dispersion of the prepolymer in water, (c) addition of a diamine-type chain extender, and (d) evaporation of the solvent in order to obtain an aqueous polyurethane dispersion containing urea functional groups.
 2. The composition as claimed in claim 1, characterized in that at said polyol component comprises at least 50% of at least one hydroxytelechelic conjugated-diene oligomer.
 3. The composition as claimed in claim 2, characterized in that said oligomer is selected from oligomers based on: butadiene, isoprene, chloroprene, 1,3-pentadiene or cyclopentadiene, or on mixtures thereof.
 4. The composition as claimed claims 2, characterized in that said oligomer has a number-average molecular weight M_(n) of 500 to 15 000
 5. The composition as claimed in claim 2, characterized in that said oligomer has a hydroxyl number expressed in meq/g of 0.5 to
 5. 6. The composition as claimed in claim 1, characterized in that said diol includes at least one neutralized acid functional group.
 7. The composition as claimed in claim 6, characterized in that said diol is triethylamine-neutralized dimethylolpropionic acid.
 8. The composition as claimed in claim 1, characterized in that said polyisocyanate component comprises at least one aliphatic, aromatic or cycloaliphatic polyisocyanate having a functionality of at least two.
 9. The composition as claimed in claim 1, characterized in that, the proportions of the polyisocyanate component and of the polyol component are such that the overall NCO/OH ratio is between 1.5 and 2.5.
 10. The composition as claimed in claims 1, characterized in that said aqueous polyurethane dispersion is obtained with a chain extender selected from diamines.
 11. The composition as claimed in claim 1, characterized in that said polyurethane represents from 2 to 50% by weight relative to the total asphalt+polyurethane weight, the weight being expressed as dry matter.
 12. (canceled)
 13. A method comprising blending of: i) at least one aqueous asphalt dispersion and ii) at least one aqueous dispersion of at least one polyurethane prepared according to the following steps: (a) formation of a prepolymer having NCO functional groups by reaction in a solvent of a polyisocyanate component, and a polyol component comprising a diol containing at least one neutralized acid functional group, (b) dispersion of the prepolymer in water, (c) addition of a diamine-type chain extender, and (d) evaporation of the solvent in order to obtain an aqueous polyurethane dispersion containing urea functional groups.
 14. The method of preparation as claimed in claim 13, characterized in that the weight proportion of the polyurethane dispersion represents from 2 to 75% of the total of asphalt and polyurethane dispersions, the asphalt and polyurethane dispersions having independent solids contents varying within a range from 20 to 60% by weight of each dispersion.
 15. (canceled)
 16. (canceled)
 17. The composition as claimed in claim 16, characterized in that said coating is a protective, sealing or waterproof, soundproofing or damping coat or coating for application for roads, roofing, in buildings or in industry.
 18. A method of production of surface coats, waterproof courses under asphalt road mixes, roofing membranes, asphalt road mixes, slurry seals or cold cast mixes, agglomeration binders, protective coverings for pipes, carpet underlay impregnation and tie layers, soundproofing and damping or insulating coverings, characterized in that it comprises the following steps: a) blending of at least one aqueous asphalt dispersion with at least one aqueous dispersion of at least one polyurethane prepared by (i) formation of a prepolymer having NCO functional groups by reaction in a solvent of a polyisocyanate component, and a polyol component comprising a diol containing at least one neutralized acid functional group, (ii) dispersion of the prepolymer in water, (iii) addition of a diamine-type chain extender, and (iv) evaporation of the solvent in order to obtain an aqueous polyurethane dispersion containing urea functional groups; b) direct application of the blend obtained in step a) to the application object or substrate; c) drying/film-forming by simple water evaporation; it being optional for steps a), b) and c) to be carried out on the actual site of the application and under the ambient conditions of the application site.
 19. Coatings, surface coats, waterproof courses under asphalt road mixes, roofing membranes, asphalt road mixes, slurry seals or cold cast mixes, agglomeration binders, protective coverings for pipes, carpet underlay impregnation and tie layers, soundproofing and damping or insulating coverings obtained by the method as defined in claim
 18. 20. The composition of claim 2 characterized in that at least 80% by weight of said polyol component consists of at least one hydroxytelechelic conjugated-diene oligomer.
 21. The composition of claim 4 wherein said M_(n) is 1000 to
 3000. 22. The composition of claim 5 wherein said hydroxyl number expressed in meq/g is 0.7 to 1.8. 